1. Field of the Invention
The present invention relates generally to hydraulic couplings used in undersea drilling and production applications. More particularly, the invention involves an undersea hydraulic coupling member with a primary poppet valve and a secondary poppet valve for higher reliability against leakage when the coupling is not mated.
2. Description of Related Art
Subsea hydraulic couplings are old in the art. The couplings generally consist of a male member and a female member, with soft seals positioned within the female member to seal the junction between the male and female members. The female member is generally a cylindrical body with a relatively large diameter longitudinal bore at one end and a relatively small diameter longitudinal bore at the other. The small bore facilitates connections to hydraulic lines, while the large bore contains soft seals and receives the male portion of the coupling. The male member includes a cylindrical portion, or probe, at one end having a diameter approximately equal to the diameter of the large bore of the female portion of the coupling. The male member also includes a connection at its other end to facilitate connection to hydraulic lines. When the cylindrical portion of the male member is inserted into the large bore of the female member, according to the various embodiments of the device, the soft seals, or O-rings, either abut the end or face of the male member or engage the cylindrical probe wall about its outer circumference. The hydraulic fluid is then free to flow through the female and male members of the coupling and seals prevent that flow from escaping about the joint and the coupling.
Poppet valves may be installed in the female member and in the male member of the coupling. Each poppet valve closes when the coupling is broken so as to prevent fluid from leaking out of the system of which the coupling is a part. Springs or other bias means have been used to urge the poppet valves into the normally closed position.
Recently, one or more pressure energized metal seals have been used in undersea hydraulic couplings of the foregoing type. For example, U.S. Pat. Nos. 4,694,859 and 5,762,106 to Robert E. Smith III, assigned to National Coupling Company, Inc. show undersea hydraulic couplings with radial metal seals that engage the diameter of the probe or male member.
In subsea hydraulic systems of the foregoing type, it is important to prevent or minimize leakage of hydraulic fluid from each of the couplings and hydraulic systems of which the couplings are a part. It also is important to prevent or minimize the entry of seawater into the couplings and hydraulic systems. While pressure energized metal seals have been effectively used to stop leakage when the couplings are mated, it is nevertheless possible that leakage may occur around the poppet valve of one or both coupling members when they are not mated. For example, debris external to the hydraulic system, or in the hydraulic system, may become lodged in or around the poppet valve when the coupling members are separated. If that occurs, there is a potential for leakage of hydraulic fluid through the coupling member because the poppet valve has not closed and sealed properly against the valve seat in the coupling member.
Leakage of hydraulic fluid from one or both coupling members poses potential serious environmental risks as well as loss of subsea system hydraulic function. Therefore, efforts have been made to reduce or eliminate leakage by assuring that the valves are closed and sealed when the coupling members are not mated. For example, U.S. Pat. Ser. No. 09/293,554 to Robert E. Smith III assigned to National Coupling Company, Inc. discloses and undersea hydraulic coupling that includes a larger spring to help urge the poppet valve closed against the seal seat and prevent or minimize leakage when the coupling members are disconnected.
It is desirable to provide an improved apparatus for ensuring that hydraulic fluid does not leak out of one or both coupling members when coupling members are separated. It is also desirable to provide an undersea hydraulic coupling with higher reliability for shutting off the flow of hydraulic fluid when the coupling members are disconnected subsea.